Tunable photoactive compounds

ABSTRACT

Photoactive compositions of matter, methods for their design and synthesis, and various applications of such compositions of matter are disclosed. Such photoactive compositions may, for example, include any one or more of the following: a core moiety; a primary electron donor moiety; an electron-withdrawing moiety; and an alkyl tail. Some photoactive compositions may further include multiple additional electron donor moieties, electron-withdrawing moieties, and alkyl tails. Applications of such photoactive compositions of matter may include use in photovoltaic cells (e.g., as a p- or n-type material of the active layer of some photovoltaic cells, or as a dye to be employed in other photovoltaic cells); batteries, field-effect transistors; and light-emitting diodes.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/839,349, entitled “Tunable Photoactive Compounds,” which was filed onMar. 15, 2013, the entire disclosure of which is incorporated herein byreference.

BACKGROUND

Use of photovoltaics (PVs) to generate electrical power from solarenergy or radiation may provides many benefits, including, for example,a power source, low or zero emissions, power production independent ofthe power grid, durable physical structures (no moving parts), stableand reliable systems, modular construction, relatively quickinstallation, safe manufacture and use, and good public opinion andacceptance of use.

SUMMARY

An emerging sector of photovoltaic (“PV”) technologies is based onorganic materials which act as light absorbers and semiconductors inlieu of legacy materials like silicon. Organic electronics promiseflexible, robust devices that can be fabricated cheaply by methods suchas roll-to-roll printing. This has been demonstrated to dateindustrially with organic light-emitting diodes common today in mobiledevices. Recent strides in Organic PV (“OPV”) technologies have reachedperformance levels approaching that of their inorganic, legacycounterparts; however, the cost of the specialty chemicals utilized aslight-absorbers and semiconductors, such as Ruthenium-based dyes, hasbeen prohibitive in bringing OPVs to market.

The present disclosure relates generally to relatively low-costphotoactive compositions of matter, as well as apparatuses and methodsfor use of the photoactive compositions of matter in OPV cells toconvert solar radiation to electrical energy. These compositions ofmatter may be deployed in a variety of OPV devices, such asheterojunction cells (e.g., bilayer and bulk), hybrid cells (e.g.,organics with ZnO nanorods or PbS quantum dots), and DSSCs(dye-sensitized solar cells). The latter, DSSCs, exist in three forms:solvent-based electrolytes, ionic liquid electrolytes, and solid-statehole transporters. These compositions may also advantageously be used inany organic electronic device, including but not limited to batteries,field-effect transistors (FETs), and light-emitting diodes (LEDs). Thepresent disclosure further provides methods for designing suchcompositions of matter, in some embodiments allowing tunability of thecompositions to obtain desirable characteristics in differentapplications.

The flexibility of the design and tunability of the photoactivecompositions of the present disclosure may allow for a wide variety ofpotential sources of synthetic material consistent with the presentdisclosure. In some embodiments, the petroleum by-product “asphaltenes”provides a desirable source of materials for design and synthesis of thephotoactive compounds of the present disclosure. Asphaltenes are rich inaromatic complexes, yet cheap and abundant, making them in some cases anideal source for such photoactive materials. Of the myriad of chemicalcompounds contained within asphaltenes, several are of particularinterest in the synthesis of light-absorbing molecules for use in OPVand other organoelectric devices including heterojunction, hybrid, andDSSC OPVs, as well as batteries, FETs and LEDs. Thus, in someembodiments, the compositions of the present disclosure may be derivedfrom asphaltene materials such as fluorenes, naphthalenes,benzothiophenes, dibenzothiophenes, naphthothiophenes,dinaphthothiophenes, benzonaphthothiophenes, benzenes, benzothiazoles,benzothiadiazoles, cyclopentabisthiophenes, and thienothiophenes.

In some embodiments, the present disclosure provides a method fordesigning a tunable photoactive compound. This method may in someembodiments include selecting a core moiety; selecting an applicationfor the compound; selecting an electron-withdrawing moiety; calculatingelectronic properties of the compound; synthesizing the compound;testing the compound; and optimizing the compound. In some embodiments,the method may further include selecting a primary electron donor moietyand calculating electronic properties of the compound. In someembodiments, the method may further include selecting a second electrondonor moiety and calculating electronic properties of the compound. Insome embodiments, the method may further include selecting a secondelectron-withdrawing moiety and calculating electronic properties of thecompound. In some embodiments, any or all of the selections may be madebased at least in part upon a corresponding electronic propertycalculation or calculations. In some embodiments, any or all selectionsmay be iteratively repeated based at least in part upon a correspondingelectronic property calculation or calculations.

In some embodiments, the present disclosure provides a chemical compoundincluding: a primary electron donor moiety; a core moiety; a secondelectron donor moiety; an electron-withdrawing moiety; and an alkyltail; wherein the primary electron donor moiety is covalently bonded tothe core moiety, the core moiety is covalently bonded to the secondelectron donor moiety, and the second electron donor moiety iscovalently bonded to the electron-withdrawing moiety. In someembodiments, the present disclosure provides a chemical compound havingthe structural formula:

In other embodiments, the present disclosure provides a chemicalcompound having the structural formula:

wherein R₁ includes a primary electron donor moiety including at leastone substituent selected from the group consisting of: aryl amine; arylphosphine; aryl arsine; aryl stibine; aryl sulfide; aryl selenide;phenyl; phenol; alkoxy phenyl; dialkoxy phenyl; and alkyl phenyl; andwherein R₂ includes a first alkyl tail including three or more carbonatoms; and wherein R₃ includes a second alkyl tail including three ormore carbon atoms.

In some embodiments, the present disclosure provides a photovoltaic cellincluding a first electrode, an active layer including a photoactiveorganic compound, and a second electrode; wherein the active layer isbetween the first and second electrodes; and wherein the photoactiveorganic compound includes a primary electron donor moiety, a coremoiety, a second electron donor moiety, an electron-withdrawing moiety,and an alkyl tail. In some embodiments, the primary electron donormoiety is covalently bonded to the core moiety, the core moiety iscovalently bonded to the second electron donor moiety, and the secondelectron donor moiety is covalently bonded to the electron-withdrawingmoiety.

In other embodiments, the present disclosure provides a photovoltaiccell including a first electrode, an active layer including aphotoactive organic compound, and a second electrode; wherein the activelayer is between the first and second electrodes; and wherein thephotoactive organic compound includes a chemical compound having thestructural formula:

In other embodiments, the present disclosure provides a photovoltaiccell including a first electrode, an active layer including aphotoactive organic compound, and a second electrode; wherein the activelayer is between the first and second electrodes; and wherein thephotoactive organic compound includes a chemical compound having thestructural formula:

wherein R₁ includes a primary electron donor moiety including at leastone substituent selected from the group consisting of: aryl amine; arylphosphine; aryl arsine; aryl stibine; aryl sulfide; aryl selenide;phenyl; phenol; alkoxy phenyl; dialkoxy phenyl; and alkyl phenyl; andwherein R₂ includes a first alkyl tail including three or more carbonatoms; and wherein R₃ includes a second alkyl tail including three ormore carbon atoms.

The features and advantages of the present disclosure will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general design scheme for a photoactive composition ofmatter of some embodiments of the present disclosure.

FIG. 2 is a general design scheme for a photoactive composition ofmatter of some embodiments of the present disclosure.

FIG. 3 is a general design scheme for a photoactive composition ofmatter of some embodiments of the present disclosure for use as a DSSCdye or BHJ semiconductor.

FIG. 4 is a chemical structure for the compound(Z)-2-cyano-3-[9,9′-diethyl-7-(N-phenylanilino)fluoren-2-yl]prop-2-enoicacid according to some embodiments of the present disclosure.

FIG. 5 is a chemical structure for2-[[9,9′-diethyl-7-(N-phenylanilino)fluoren-2-yl]methylene]propanedinitrileaccording to some embodiments of the present disclosure

FIG. 6 depicts an exemplary method for designing photoactive compoundsaccording to some embodiments of the present disclosure.

FIG. 7 is a chemical structure for(E)-2-cyano-3-[9,9-diethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid according to some embodiments of the present disclosure.

FIG. 8 is a chemical structure for(E)-2-cyano-3-[9,9-diethyl-7-[N-(1-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid.

FIG. 9 is a graph containing data derived from computations carried outby molecular modeling software, and which shows the LUMO and HOMOvalues, in eV, of(E)-2-cyano-3-[9,9-diethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid versus(E)-2-cyano-3-[9,9-diethyl-7-[N-(1-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid.

FIG. 10 is a chemical structure for(E)-2-cyano-3-[9,9-dihexyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid according to some embodiments of the present disclosure.

FIG. 11 is an illustration of molecular stacking that results from thepresence of aromatic hydrocarbons according to some embodiments of thepresent disclosure.

FIG. 12 is an illustration of intermolecular spacing achieved throughthe addition of one or more alkyl tails to molecules comprising aromatichydrocarbons, according to some embodiments of the present disclosure.

FIG. 13 is a depiction of the alignment of dye molecules on TiO₂surface.

FIG. 14 a is a space-filling model of(E)-2-cyano-3-[9,9-diethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid, according to some embodiments of the present disclosure.

FIG. 14 b is a space-filling model of(E)-2-cyano-3-[9,9-dihexyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid, according to some embodiments of the present disclosure.

FIG. 15 is an illustration of DSSC design depicting various layers ofthe DSSC according to some embodiments of the present disclosure.

FIG. 16 is another illustration of DSSC design depicting various layersof the DSSC according to some embodiments of the present disclosure.

FIG. 17 is a chemical structure for(E)-2-cyano-3-[9,9-diethyl-7-[2-naphthyl(phenyl)phosphanyl]fluoren-2-yl]prop-2-enoicacid according to some embodiments of the present disclosure.

FIG. 18 is a chemical structure for(E)-2-cyano-3-[9,9-diethyl-7-(2-naphthylsulfanyl)fluoren-2-yl]prop-2-enoicacid according to some embodiments of the present disclosure.

FIG. 19 illustrates chemical structures for(E)-2-cyano-3-[9,9′-R,R′-7-[N-(2-naphthypaniline]fluoren-2-yl]prop-2-enoicacid, where R signifies a dialkyl tail of various isomers of C₂ to C₁₀compounds, according to some embodiments of the present disclosure.

FIG. 20 illustrates chemical structures for various embodiments of thepresent disclosure, labeled T2, T3, T4, T5, T6, and T7.

FIG. 21 is a graph containing data derived from computations carried outby molecular modeling software, and which shows HOMO and LUMO values ofT2, T3, T4, and T5 of FIG. 20.

FIG. 22 is a graph containing data derived from computations carried outby molecular modeling software, and which shows HOMO and LUMO values ofT6 and T7 of FIG. 20.

FIG. 23 is an example synthetic pathway for the formation of(Z)-2-cyano-3-[9,9′-diethyl-6-[N-(2-naphthyl)aniline]fluoren-3-yl]prop-2-enoicacid, according to some embodiments of the present disclosure.

FIG. 24 a is an example illustration of DSSC design according to someembodiments of the present disclosure.

FIG. 24 b is an example illustration of BHJ device design according tosome embodiments of the present disclosure.

FIG. 25 is a representation of relative energy levels in eV of variouscomponents of an exemplar DSSC system that uses an iodide electrolyteaccording to some embodiments of the present disclosure. The data ofFIG. 25 is derived from empirical results such as cyclic voltammetry orultraviolet photoelectron spectroscopy.

FIG. 26 is a schematic view of a typical photovoltaic cell including anactive layer according to some embodiments of the present disclosure.

FIG. 27 is an exploded, representational view of a sample PV cell havinga transparent conducting electrode, an electron blocking layer, a p-typethin film active layer, an n-type organic active layer, a hole blockinglayer, and a low work-function layer according to some embodiments ofthe present disclosure.

FIG. 28 is a schematic of a typical solid state DSSC device according tosome embodiments of the present disclosure.

FIG. 29 is a representation of relative energy levels in eV of variouscomponents of an exemplar solid state DSSC system that uses asolid-state layer in accordance with some embodiments of the presentdisclosure. The data of FIG. 29 is derived from empirical results suchas cyclic voltammetry or ultraviolet photoelectron spectroscopy.

FIG. 30 is a representation of relative energy levels in eV of variouscomponents of another exemplar solid state DSSC system that uses asolid-state layer in accordance with some embodiments of the presentdisclosure. The data of FIG. 30 is derived from empirical results suchas cyclic voltammetry or ultraviolet photoelectron spectroscopy.

FIG. 31 is a chemical structure for(E)-2-cyano-3-[6-[9,9-diethyl-7-(4-methoxy-N-(4-methoxyphenyl)anilino)fluoren-2-yl]benzothiophen-2-yl]prop-2-enoicacid.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure relates generally to compositions of matter,apparatus and methods of use of materials in organic photovoltaic cellsin creating electrical energy from solar radiation. More specifically,this disclosure relates to photoactive compositions of matter, as wellas apparatus and methods of use and formation of such compositions ofmatter, as well as methods for designing photoactive compositions ofmatter. In some embodiments, the present disclosure provides uses ofphotoactive compositions of matter in OPV devices includingheterojunction cells, hybrid cells, and DSSCs. In embodiments concerningDSSCs, said photoactive compositions are compatible with traditionalsolvent-based electrolytes of I₂ or Co complexes, but additionallysolid-state DSSC structures free of electrolyte, containing ratherhole-transport materials such as spiro-OMeTAD or CsSnI₃. In otherembodiments, the photoactive compositions of matter may be used in anyorganic electronic device, including but not limited to batteries,field-effect transistors (FETs), and light-emitting diodes (LEDs). Thephotoactive compositions of matter may, in some embodiments, be employedwith additives (such as, in some embodiments, chenodeoxycholic acid or1,8-diiodooctane).

In some embodiments, the present disclosure provides small-moleculephotoactive compositions of matter. In some embodiments, thecompositions of matter may be based upon polymeric or oligomericmaterials. As used herein, “small-molecule” or “small molecule” refersto a finite molecular structure (e.g., acetone or benzene). It could, insome cases, also be referred to as a monomeric unit.

Referring to FIG. 1, in some embodiments, the compositions of matter ofthe present disclosure generally include: a primary electron donormoiety 2 a core moiety 1, and an electron withdrawing moiety 3. In someembodiments, the primary electron donor moiety 2 is chemically bound tothe core moiety 1, and the core moiety is chemically bound to theelectron-withdrawing moiety 3. In some embodiments, the electron donormoiety is located on the opposing end of the photosensitive compoundfrom the electron-withdrawing moiety. In some embodiments, electronsgenerally flow within the photoactive composition from the primaryelectron donor moiety, to the core moiety, to the second electron donormoiety (if present), to the electron-withdrawing moiety, in accordancewith the electron flow 4 depicted in FIGS. 1, 2, and 3.

In some embodiments, the compositions of matter optionally may furthercomprise a second electron donor moiety 5, as shown in FIG. 2. In someembodiments, the primary electron donor moiety 2, core moiety 1, andelectron withdrawing moiety 3 may be bonded to each other in the ordershown in FIG. 1. In other embodiments, the second electron donor moiety5 may be between the core moiety 1 and the electron-withdrawing moiety3, as shown in FIG. 2. And in some embodiments, the electron-withdrawingmoiety 3 may comprise a substituent capable of binding the photoactivecomposition to another substance 6, as shown in FIG. 3. In someembodiments, this substance 6 may be a mesoporous layer of a DSSC (whichmay be, for example, TiO₂). In some embodiments, the compositions ofmatter may comprise a second electron-withdrawing moiety instead of orin addition to a second electron donor moiety. In yet other embodiments,the composition may comprise three or more electron-withdrawing moietiesbonded to each other. In some embodiments, each electron-withdrawingmoiety may instead be located anywhere in the composition.

As used herein, “moiety” refers to the most general term to identify amolecular fragment (e.g., tri-aryl amine). It may include, but notnecessarily be limited to, a substituent and/or a functional group. A“substituent” is any partial, identifiable fragment bonded (covalently,ionically, or otherwise) to a parent molecule (e.g., a methyl group),and a “functional group” is a molecular group that may be used to definethe parent molecule (e.g., carboxylic acid). Thus, a substituent mayinclude, but not necessarily be limited to, a functional group, andvice-versa. In addition, electron donor and electron-withdrawingmoieties may generally be referred to as electron-rich andelectron-poor, respectively.

Molecular Tunability and Composition Design

In some embodiments, the core moiety 1 intrinsically has all necessarycharacteristics to be employed in the various applications of thephotoactive compositions of the present disclosure, such as a dye for aDSSC, or as a LED, or in any other application consistent with thisdisclosure as laid out previously. The photoactive compositions of theseembodiments comprise the additional components identified in FIG. 1(that is: a primary electron donor moiety 2, one or more electronwithdrawing moieties 3, and, in some embodiments, an optional secondelectron donor moiety 5) in order to enhance or otherwise modify theintrinsic characteristics of the core moiety 1. These compositions, insome embodiments, further comprise one or more alkyl tails (for example,the 9,9-diethyl moieties 410 appended to the fluorene moiety 415 of FIG.4 are alkyl tails of one embodiment, as are the 9,9-diethyl moieties 510appended to the fluorene moiety 515 of FIG. 5). These additionalcomponents (primary and second electron donor moieties, electronwithdrawing moiety, and alkyl tail or tails) may in some embodimentsprovide for a high degree of molecular tunability, allowing eachcomposition of these embodiments to be finely tuned to its application,including obtaining desired properties relating to the composition'selectronic properties, which include, but are not limited to: absorptionwindow, molecular orbital energy levels (including band gap E_(g), HOMO(Highest Occupied Molecular Orbital) and LUMO (Lowest UnoccupiedMolecular Orbital) energy levels), and adjustment of intermolecularinteractions such as intermolecular spacing. In some embodiments,selection and incorporation of these additional components may provideor affect additional electronic properties or other characteristics,such as the capability of bonding to another surface, molarabsorptivity, modifying the molecular dipole, electron-donating andwithdrawing capabilities, and generation and maintenance of excitons,among others. As used herein, “electronic properties” include anyproperty or characteristic of a molecule that one of ordinary skill inthe art would recognize as affecting or otherwise modifying a molecule'selectronic, photoactive, conducting, dielectric or semiconductingcharacteristics.

Accordingly, some embodiments of the present disclosure provide methodsfor designing a photoactive composition comprising sourcing a coremoiety, and further comprising selection of the additional components soas to tune the composition by enhancing the electronic properties of thephotoactive composition as compared to the electronic properties of thecore moiety alone.

The methods of selection of some embodiments comprise selectingcomponents based upon one or more tunability considerations. Tunabilityconsiderations may, in some embodiments, comprise any one or moreelectronic properties. Non-limiting examples of such properties of thephotoactive composition sought to be designed include: HOMO (HighestOccupied Molecular Orbital) energy level; LUMO (Lowest UnoccupiedMolecular Orbital) energy level; band gap (E_(g)), which is thedifference between HOMO and LUMO energies; absorption window (i.e., theallowed absorption wavelengths based on the band gap E_(g)); addition ofsemiconducting or conducting characteristics to the photoactivecomposition; polarizability; molar absorptivity; intermolecular spacingof the photoactive composition; oxidation susceptibility; reductionsusceptibility; chiralty or achiralty; exciton formation; excitonmaintenance; molecular dipole moment; heat of solvation; structuralvolume; heat of formation; V_(OC) (open-circuit voltage); J_(SC)(Photocurrent density); Fill Factor percentage (FF %); andlight-to-power conversion efficiency (PCE). Tunability considerationsmay, in some embodiments, further or instead comprise any otherelectronic property or properties of the photoactive composition soughtto be designed. Although several such properties are expressly mentionedherein, one of ordinary skill in the art with the benefit of thisdisclosure would be capable of taking into account any other electronicproperty or properties in tunability considerations.

Tunability considerations of some embodiments may in addition or insteadcomprise any one or more of various conditions in the environment inwhich the photoactive composition is used or intended to be used. Suchenvironmental conditions may, in some embodiments, comprise any one ormore of the following: the presence of a solvent; the identity of thesolvent (if present); the concentration of the photoactive compositionin solution with a solvent (if present); the presence of a surface orother substance to which the photoactive composition is or is intendedto be bonded, absorbed, adsorbed, or otherwise chemically or physicallyattached to a surface (such as, in some embodiments, TiO₂); the presenceof additives (such as, in some embodiments, chenodeoxycholic acid or1,8-diiodooctane).

Tunability considerations may be taken into account in the methods ofsome embodiments in various ways. In some embodiments, in order tomodify the core moiety intrinsic characteristics, the additionalcomponents are selected for addition to the core moiety via covalentbonding in order to produce a photoactive composition with enhanced orotherwise modified properties. In some embodiments, to make thephotoactive composition easier to oxidize and more difficult to reduce,electron-donating moieties are selected for addition to the composition;this can also, in some embodiments, induce p-type semiconductingcharacter. Further, in some embodiments, one or moreelectron-withdrawing moieties are selected for addition in order to makethe composition more difficult to oxidize and easier to reduce; this canalso, in some embodiments, induce n-type semiconducting character. Inother embodiments, electron-donating and electron-withdrawing moieties,2 and 3, respectively, can be selected for addition together on oppositeends of the composition, as in FIG. 1, to fine-tune the molecularelectronic characteristics beyond what either moiety can do alone. Forexample, a smaller band gap E_(g) may result from addition of both anelectron-donating and electron-withdrawing moiety than would result fromthe presence of only one of those two components. Additionally, in someembodiments, the motif illustrated in FIG. 1 can be designed to create amolecular dipole 4 of desired magnitude and direction (molecular dipolesare vector quantities). Further, in other embodiments, moieties such asalkyl chains, carboxylic acid groups, or aromatic groups can be selectedand added to induce molecular ordering on a surface, such as Au, Ag, FTO(fluorine-doped tin oxide), ITO (indium tin oxide), Nb₂O₅ or TiO₂, as alayer or into supramolecular extended structures, such as metal organicframeworks, covalent organic frameworks, or crystalline structures.

Tunability considerations are taken into account in the design methodsof other embodiments in order to maximize or otherwise alter theelectronic properties of the photoactive composition. For instance, insome embodiments, it is desirable to minimize the band gap (E_(g)),which as noted above is the energy difference between the HOMO energiesand the LUMO energies, in order to red shift the light absorptionmaximum and therefore achieve increased current in the photoactivecomposition through a broader spectral window. In some embodiments, thismay comprise creating a deeper (that is, greater absolute value in eV)LUMO level energy, for example to facilitate electron transfer from anelectron donor or electrode. In other embodiments, a deeper HOMO isdesired, for example to allow unimpeded hole transfer to anothersemiconducting material or to an electrode. In some embodiments, it isbeneficial to have a shallower LUMO energy, for example to allowelectron transfer to an electron accepting material or electrode. Inother embodiments, it is beneficial to have a shallower HOMO energy, forexample to facilitate the acceptance of a hole from a semiconductingmaterial or electrode.

The methods of other embodiments may comprise tuning the composition'sband gap E_(g), its absorption window, or both, by selecting and/orincorporating any one or more of the following into the composition: aprimary electron donor moiety, a second electron donor moiety, anelectron-withdrawing moiety, and a second electron-withdrawing moiety.The methods of yet other embodiments may comprise selecting and/orincorporating more than two of either or both of electron donor moietiesand electron-withdrawing moieties. Any one or more other tunabilityconsiderations may also or instead be accounted for by selecting and/orincorporating any one or more of the primary electron donor moiety,second electron donor moiety, and electron-withdrawing moiety. Themethods of some embodiments may further comprise tuning thecomposition's intermolecular interactivity by selecting andincorporating one or more alkyl tails. The methods of other embodimentsmay comprise tuning the composition's intermolecular interactivity byselecting and incorporating any one or more of the core moiety or anyadditional component. For example, in some embodiments, carboxylic acidsmay cause molecules of the photoactive composition to dimerize. In otherembodiments, for example, a primary electron donating moiety comprisingan anthracene moiety instead of a naphthyl moiety may increase theattraction between two molecules of the photoactive composition.

Selection of one or more electron donor moieties and/orelectron-withdrawing moieties may, in some embodiments, be carried outin order to alter the band gap E_(g) of the photoactive composition.This may be accomplished, for example, by modifying either or both ofthe HOMO or LUMO. For example, in some embodiments, a shallower HOMO(that is, greater electron density) for the photoactive composition as awhole is desirable. In such embodiments, a primary electron donor moietythat is selected and incorporated into the photoactive composition maycomprise any one or more of the following: alkyl amines, alkyl arylamines, and aryl amines. The primary electron donor moieties of otherembodiments may be selected and incorporated such that they comprise anyone or more of the following: anisole aryl amines, including otheralkoxy derivatives greater than methyl, di- and tri-alkyl derivatives;alkyl and other hydrocarbon phenyl substituents; halogen substituents;and either p-, o-, or m-covalent bonding. In other embodiments, theelectron-withdrawing moiety may be selected and incorporated in order toadjust the LUMO. For example, in order to make the LUMO very shallow, astrong electron-withdrawing moiety (that is, an electron-withdrawinggroup with a greater electron affinity relative to other moieties of thephotoactive composition) should be selected. Examples of strongelectron-withdrawing moieties include any one or more of the following:dicyanomethane, cyano acrylate, dicarboxylic acid, as well as halogenacrylates. Weaker electron-withdrawing moieties (that is,electron-withdrawing moieties that would make the LUMO less shallow)include, but are not limited to, any one or more of the following:carboxylic acid, amides, esters, and halogenated hydrocarbons. In someembodiments wherein alteration of the E_(g) is desired (by, for example,making E_(g) smaller), alteration of only one of the LUMO or HOMO energylevel may be targeted. In some embodiments, various tunabilityconsiderations may be inter-dependent (that is, at least one tunabilityconsideration may depend on at least one other tunabilityconsideration).

The following example illustrates the interplay and specificity of thetunability considerations of some embodiments. FIG. 25 is arepresentation of relative energy levels in eV of various components ofan exemplar DSSC system that uses an iodide electrolyte: FTO(fluorine-doped tin oxide); TiO₂ (titanium dioxide); T2 (an embodimentof a photoactive compound of the present disclosure); iodide electrolyte(illustrated by oxidation reactions I⁻→I₂ ⁻ and I₂ ⁻→I₃ ⁻); and theAnode. The data shown in FIG. 25 was derived from empirical results suchas cyclic voltammetry or ultraviolet photoelectron spectroscopy. In FIG.25, relative conduction band and LUMO energy values of TiO₂ and T2 (4.14and 2.85, respectively) are toward the top of the graph, and valenceband and HOMO energy values are toward the bottom (7.44 and 5.36,respectively), with eV values of iodide electrolyte reduction of T2 andeV values at the Anode and FTO also being shown. The T2 is employed inthis example embodiment as a DSSC dye. As can be seen in FIG. 25,shallower HOMO energies in T2 would not allow for reduction of theoxidized T2 by the I₂ ⁻→I₃ ⁻ couple, so a shallower HOMO energy levelwould not be desired. However, a deeper LUMO energy level would resultin a reduction in E_(g) in the T2, which could in some embodiments leadto a greater PCE. Thus, the nature of the application in which thephotoactive composition is deployed may provide additional tunabilityconsiderations, demonstrating in this example that modification of thedesign of T2 should target deeper LUMO energy levels but not shallowerHOMO energy levels. In other instances—such as use in a solid-state DSSCin accordance with some embodiments of the present disclosure—thephotoactive compound may be designed to target shallower HOMO energylevels due to the presence of, for example, a solid electrolyte (asopposed to a liquid electrolyte such as the iodide electrolyte depictedin FIG. 25). FIG. 29, for example, shows the shallower HOMO energy levelof a solid electrolyte of some embodiments (CsSnI₃), which permits aphotoactive compound of the present disclosure (e.g., T2, as shown inFIGS. 25 and 29) to be designed with a shallower HOMO. Thus, the use ofa solid electrolyte could, in some embodiments, open greater designpossibilities and permit targeting a shallower HOMO energy level (andtherefore, in some embodiments, an even smaller E_(g)). This couldprovide significant advantages in the PCE values of solid state DSSCsemploying a photoactive composition of matter according to the presentdisclosure. FIG. 29 and solid-state DSSC embodiments are discussed ingreater detail elsewhere in this disclosure.

In some embodiments, selection of any one or more of the primaryelectron donor moiety, the second electron donor moiety, and theelectron-withdrawing moiety may have effects on the overall photovoltaicpower conversion efficiency (PCE) of the photoactive composition whenused in, for example, OPV applications. In some embodiments, it may bedesirable to design the composition so as to maximize its PCE when usedin OPV applications. The effects on the PCE of various design elementsalone or in combination with other design elements may not be readilydeterminable without calculation and experimentation. Thus, the presentdisclosure further provides, in some embodiments, a method for carryingout the necessary experimentation and calculation to optimize selectionof any one or more of: the core moiety, the electron-withdrawing moiety,the primary electron donor moiety, and the second electron donor moiety.Therefore, such calculation and experimentation would be routine to oneof ordinary skill in the art with the benefit of this disclosure.

Referring to FIG. 6, this method, in some embodiments, may comprise aphotoactive core moiety selection step 601. In some embodiments, thisstep 601 may further comprise selecting a photoactive core moiety fromasphaltenes. Thus, for example, a range of potentially useful coremoieties selected from asphaltenes may include, but not necessarily belimited to, any one or more of the following: fluorene, benzothiophene,dibenzothiophene, naphthothiophene, dinaphthiophene, andbenzonaphthothiophene.

In other embodiments, the method may further comprise an applicationselection step 602 comprising, in some embodiments, determining one ormore applications for the photoactive composition (e.g., BHJ, DSSC,FET). In some embodiments, the method may further comprise anelectron-withdrawing moiety selection step 603. In some embodiments, theelectron-withdrawing moiety is selected based at least in part upon theapplication selected at 602. For example, in embodiments wherein DSSC isselected at 602, it may be desirable to select an electron-withdrawingmoiety that comprises a carboxylic acid substituent, which may enablebonding to another surface, examples of which include, but are notlimited to, Au, Ag, FTO (fluorine-doped tin oxide), ITO (indium tinoxide), Nb₂O₅, or TiO₂ as a layer or into supramolecular extendedstructures, such as metal organic frameworks, covalent organicframeworks, or crystalline structures. In other embodiments, anelectron-withdrawing moiety comprising a cyanoacrylate, boronic acid,sulfate, phosphate, nitrate, halogen silane, or alkoxy silane may beselected to enable surface bonding. Furthermore, in some embodiments,notwithstanding the depiction of FIG. 6, the application selection step602 may be carried out prior to the core moiety selection step 601.

In some embodiments, the method may further comprise a first electronicproperty calculation step 604, which may comprise calculating theelectronic properties of a composition comprising the core moietyselected at step 601 and the electron-withdrawing moiety selected atstep 603. Electronic properties calculated in this step may, in someembodiments, include the electronic properties previously discussed andwhich are calculable. Thus, in some embodiments, electronic propertiescalculated in this step may comprise any one or more of the following:HOMO structure, LUMO structure, HOMO energy, LUMO energy, band gapE_(g), molar absorptivity, allowed absorption wavelengths,intermolecular spacing, molecular dipole, heat of solvation, structuralvolume, and heat of formation. In some embodiments, other electronicproperties already discussed may also be calculated in this step.

In some embodiments, the method may further comprise a primary electrondonor moiety selection step 605, which in some embodiments may be basedat least in part upon the result of the electronic property calculationstep 604. In some embodiments, the primary electron donor is selected inorder to modify the HOMO of the photoactive composition. In addition,the method of some embodiments may further comprise a second electronicproperty calculation step 606, which comprises calculating theelectronic properties of the composition comprising the core moietyselected at step 601, the electron-withdrawing moiety selected at step603, and the primary electron donor moiety selected at step 605.

This second electronic property calculation step 606 may, in someembodiments, be iteratively repeated in alternation with the primaryelectron donor moiety selection step 605, such that a different primaryelectron donor moiety is selected based at least in part upon theresults of the second electronic property calculation step 606, followedby another iteration of the second electronic property calculation step606, which may in some embodiments lead to again repeating the primaryelectron donor selection step 605. In some embodiments, this repetitioncontinues until a desired result of the second electronic propertycalculation step 606 is reached. Desired results of the secondelectronic property calculation step may, in some embodiments, be basedupon the tunability considerations previously discussed. Thus, returningto the example of minimizing the band gap (E_(g)) in order to red shiftthe light absorption maximum and therefore achieve increased current inthe photoactive composition through a broader spectral window, a desiredresult would therefore comprise a minimized band gap E_(g) value. Insome embodiments, the calculation results may furthermore indicate thatoverall design goals have been met, for example, by indicating a desiredE_(g) value, PCE value, or other electronic property value has beenobtained. If this is the case, the method may in some embodimentsproceed directly to a synthesis step 609.

The method in some embodiments may comprise a second electron donor orwithdrawing moiety selection step 607. This step may in some embodimentscomprise selection of either or both of a second electron donor moietyor a second electron-withdrawing moiety. Results of the secondelectronic property calculation step 606 may, in some embodiments, format least part of the basis for determining whether a second electrondonor moiety, a second electron-withdrawing moiety, or both, should beselected at the second electron donor or withdrawing moiety selectionstep 607. Results of the second electronic property calculation step 606may also or instead form at least part of the basis for determiningwhich second electron donor moiety, second electron-withdrawing moiety,or both, should be selected. In addition, this step, in someembodiments, may further comprise a third electronic propertycalculation step 608, which comprises calculating the electronicproperties of the composition comprising any component so far selected.Thus, in some embodiments, the calculation may be based upon aphotoactive composition comprising any one or more of: the core moietyselected at step 601; the electron-withdrawing moiety selected at step603; the primary electron donor selected at step 605; and the secondelectron donor moiety and/or second electron-withdrawing moiety selectedat step 607.

This third electronic property calculation step 608 may, in someembodiments, be iteratively repeated in alternation with the secondelectron donor or withdrawing moiety selection step 607, such that adifferent second electron donor moiety, second electron-withdrawingmoiety, or both, is selected based at least in part upon the results ofthe third electronic property calculation step 608, followed by anotheriteration of the third electronic property calculation step 608, whichmay in some embodiments lead to again repeating the second electrondonor or withdrawing moiety selection step 607. In some embodiments,this repetition continues until a desired result of the third electronicproperty calculation step 608 is reached. As with the second electronicproperty calculation step 606, desired results of the third electronicproperty calculation step 608 may, in some embodiments, be based atleast in part upon tunability considerations. Again, desired values mayin some embodiments differ depending upon the tunability considerationand the target.

In some embodiments, the selection and calculation steps 601 and 603through 608 may be carried out at least in part by using molecularmodeling software. Non-limiting examples of molecular modeling softwareinclude Spartan, Jaguar, and Gaussian. Calculations are, in someembodiments, based on Density Functional Theory, method: RB3LYP, andbasis set: 6-31 G*.

The method of some embodiments may further comprise a synthesis step609. In some embodiments, this step comprises synthesizing one or moremolecules that comprise the component or components selected in any oneor more of the previous steps 601, 603, 605, and 607. In someembodiments, this synthesis step 609 is carried out once any one or moreof the first electronic property calculation step 604, the secondelectronic property calculation step 606, and the third electronicproperty calculation step 608 result in a desired value or set of valuesto meet the design goals of the photoactive composition. Design goals ofthe photoactive composition may include a desired value of any one ormore electronic properties, which in some embodiments may depend atleast in part upon the application selected for the composition at theapplication selection step 602. For example, in some embodiments, wherethe composition is to be used in a DSSC, a minimum desired PCE, such as,e.g., 7.5% may be a design goal. Other examples may include a maximumdesired band gap, or a specific HOMO and/or LUMO energy level to allowcompatible charge transfer with another substance. Design goals may alsoinclude, in some embodiments, simply the existence of a molecular dipolemoment, and in some embodiments, that dipole moment may be of a desiredminimum value.

The design goals may or may not be the same as the desired calculationresults; thus, for example, a desired calculation result of a band gapbelow a desired maximum value (in eV) might not result in a moleculethat, when applied to an OPV, would exhibit a minimum desired PCE value.Thus, in some embodiments, if, after steps 601 through 608 are performedand, although desired results of the third calculation step 608 arereached, design goals are not reached, then the method of theseembodiments may further comprise repeating any one or more of steps 601through 608 in accordance with the description of various embodimentsabove. For example, referring to FIG. 6, an embodiment is shown wherein,if design goals are not met even after the third electronic propertycalculation step 608 achieves desired results, the process repeats atthe core moiety selection step 601.

In some embodiments, the method may further comprise a testing step 610wherein, in some embodiments, the molecule or molecules are tested inthe one or more applications selected at the application selection step602.

In some embodiments, the method may further comprise an optimizationstep 611, wherein the device or application in which the photoactivecomposition is tested is optimized by various means. Such means include,but are not necessarily limited to, any one or more of the following:radiation, thermal or chemical treatments, or interfacial modificationor additives. In some embodiments, optimization may comprise theaddition of one or more alkyl tails to the photoactive composition. Insome embodiments, the alkyl tails may be added to the core moiety of thephotoactive composition.

In some embodiments, the method may further comprise repeating thetesting step 610 following optimization step 611. In some embodiments,optimization step 611 and testing step 610 may be repeated one or moretimes until ultimate goals are met. In some embodiments, after zero ormore repetitions of the alternating optimization step 611 and testingstep 610 in this manner, if ultimate goals are still not met, theprocess repeats from the beginning.

Furthermore, the method of some embodiments may additionally comprise analkyl tail selection step (not shown in FIG. 6) instead of or inaddition to alkyl tail addition, if any, in optimization step 611. Insome embodiments, this step may take place before synthesis step 609. Insome embodiments, the alkyl tail selection step may comprise selectingany one or more alkyl tails to be appended to the composition. In someembodiments, the alkyl tail or tails may be selected for addition to thecore moiety of the composition. Selection of an alkyl tail or tails maybe based at least in part upon the calculation results of any one ormore of electronic property calculation steps 604, 606, and 608. In someembodiments, the alkyl tail selection step may further compriseselecting the location on the composition at which to append the alkyltail or tails. The alkyl tail selection step also may comprise anadditional electronic property calculation step, which may be carriedout similarly to any of electronic property calculation steps 606 and608 (that is, iteratively calculating electronic properties, changingalkyl tail selection, and re-calculating electronic properties).

It will be apparent to one of ordinary skill in the art that theabove-outlined methods are merely example embodiments. Variousalterations are contemplated by this disclosure. Thus, although theexample embodiment outlined in FIG. 6 proceeds with later calculationsbased upon a selected electron-withdrawing moiety at step 603, andcontemplates selection of different primary electron donor moieties andsecond electron donor moieties depending upon results of latercalculations, the method could instead proceed whereby a differentelectron-withdrawing moiety is selected when desired calculation resultsare not met in any of steps 604, 606, or 608.

The systems and methods of the present disclosure described above may beimplemented in software to run on one or more computers, where eachcomputer includes one or more processors, a memory, and may includefurther data storage, one or more input devices, one or more outputdevices, and one or more networking devices. The software includesexecutable instructions stored on a tangible medium.

Methods of various embodiments consistent with this disclosure arefurther elaborated in the context of the below discussion of variouscomponents of the compositions of matter of certain embodiments of thepresent disclosure.

Core Moiety

In some embodiments, the core moiety may comprise fluorene. In otherembodiments, the core moiety may comprise any one of: benzothiophene,dibenzothiophene, naphthothiophene, dinaphthothiophene,benzonaphthothiophene, biphenyl, naphthyl, benzene, benzothiazole,benzothiadiazole, benzo[b]naphtha[2,3-d]thiophene,4H-cyclopenta[1,2-b:5,4-b′]bisthiophene, dinaphtho[2,3-d]thiophene,thieno[3,2-b]thiophene, naphthalene, or anthracene. In otherembodiments, the core moiety may comprise any other multi-cyclicaromatic ring. In some embodiments, the core moiety comprises a compoundor compounds extracted from asphaltenes.

Alkyl Tails and Alkyl Tail Selection

In some embodiments, the core moiety may further comprise one or morealkyl tails. In some embodiments, an alkyl tail is a substituentcomprising a carbon backbone and that is bonded to a single carbon atomof any of the following: a core moiety; a primary electron donor moiety;an electron donor moiety; and an electron-withdrawing moiety. In someembodiments, the distal end of the carbon backbone of the alkyl tail isnot covalently bonded to another compound. In some embodiments, twoalkyl tails are bonded to the same carbon atom. For example, in someembodiments in which the core moiety comprises fluorene, the core moietymay additionally comprise two alkyl tails appended at the 9,9′ carbon ofthe fluorene molecule (e.g., a 9,9′-dialkyl functionalized fluorene). Byway of example, FIG. 4 depicts a composition of some embodiments of thepresent disclosure, which includes a fluorene 415 functionalized withdiethyl alkyl tails 410 at the 9,9′ carbon of the fluorene. Similarly,the embodiment depicted in FIG. 5 includes a fluorene 515 functionalizedwith diethyl alkyl tails 510 at the 9,9′ carbon of the fluorene.Appending an alkyl tail or tails to the 9,9′ carbon of fluorene may beadvantageous because the hydrogen atoms appended thereto are acidic, andmay be more readily substituted by alkyl tails.

However, different advantages such as greater molecular spacing may beachieved by appending an alkyl tail or tails to different locations onthe core moiety, or on different locations of the photoactivecomposition, depending upon the makeup of the photoactive composition.Thus, in some embodiments, the alkyl tail or alkyl tails appended to thephotoactive composition of matter may be appended on any carbon of thecore moiety in place of one or more hydrogen atoms (that is, the alkyltail or tails replace a hydrogen or hydrogens bonded to the carbon). Thealkyl tail or tails may, in other embodiments, be appended to anycarbon, or other atom, bonded to one or more hydrogens within thephotoactive composition of matter (e.g., a carbon, or other atom, of thesubstituent that constitutes the primary electron donor moiety of someembodiments). In yet other embodiments comprising multiple alkyl tails,the alkyl tails may be appended to different carbon, or other, atomswithin the composition.

The alkyl tail or tails of some embodiments may comprise C₂ to C₁₀hydrocarbons, including various isomers. The alkyl tails of otherembodiments may comprise C₂ to C₁₅ hydrocarbons, or, in otherembodiments, C₂ to C₂₀ hydrocarbons. In yet other embodiments, the alkyltails may comprise C₂ to C₃₀ hydrocarbons, or, in other embodiments, C₂to C₄₀ hydrocarbons. As used herein, a “C₂” hydrocarbon is a hydrocarboncontaining 2 carbon atoms; a C₁₀ hydrocarbon is a hydrocarbon containing10 carbon atoms, and, in general, a C_(x) hydrocarbon is a hydrocarboncontaining x carbon atoms, where x is an integer. The alkyl tail ortails of some embodiments may comprise more than 40 carbons.

In some embodiments, the C₂ to C₁₀ hydrocarbons are linear or branchedhydrocarbon chains. Thus, the alkyl tail or tails of some embodimentsmay comprise a C₂ to C₁₀ linear chain (that is, a hydrocarbon chain thatis 2 through 10 carbon atoms long), with hydrocarbon branches of variouslengths appended to various carbons on the C₂ to C₁₀ linear chain. Thus,when an alkyl tail of some embodiments comprises a C₄ hydrocarbon, thoseembodiments may comprise any of the various possible isomers of C₄hydrocarbons. That is, a C₄ alkyl tail of some embodiments may comprisea butyl group, or it may comprise a branched alkyl tail such as amethylpropyl group. Again, various isomers of a methylpropyl group maybe used in various embodiments (e.g., the methyl group may be appendedto any carbon of the propyl group).

Returning to the example embodiments in which the core moiety comprisesa fluorene, in embodiments employing C₂ alkyl tails, the core moietycould comprise a 9,9′-diethyl fluorene. Likewise, in embodiments whereinthe alkyl tails each comprise a C₃ hydrocarbon, the core moiety of suchembodiments may comprise a 9,9′-dipropyl fluorene, or in otherembodiments (using another C₃ isomer), a 9,9′-dimethylethyl fluorene.Any other C₂ to C₁₀ isomer may be used. Or, in other embodiments, anyother C₂ to C₁₅, C₂ to C₂₀, C₂ to C₃₀, or C₂ to C₄₀ isomer may be used.FIG. 19 depicts the use of various alkyl tails on the fluorescent moietyof various embodiments of photoactive compositions, such as ethyl (C₂),decyl (C₁₀), and ethylhexyl (C₈, branched) alkyl tails.

In some embodiments, an alkyl tail or tails may provide spacing betweendifferent molecules of this photoactive composition. This may, forexample, increase the light-to-power conversion efficiencies (PCEs) ofPV cells comprising the photoactive composition. The spacing provided bythe alkyl tail or tails may vary depending upon the makeup of thephotoactive composition of some embodiments (e.g., different alkyl tailsmay be ideal for compositions comprising different primary electrondonating moieties). In addition, the alkyl tail or tails may provideenhanced solubility when the photoactive compositions of the presentdisclosure are employed in the presence of a solvent (such as, forexample, where the photoactive compositions are used or intended to beused in a DSSC, BHJ, or hybrid OPV device). The alkyl tail or tails ofsome embodiments may therefore depend upon the identity of the solventused. Possible solvents include, but are not limited to:dichlorobenzene, chlorobenzene, toluene, methylene chloride, chloroform,acetonitrile, ethanol, methanol, and water.

Thus, the present disclosure in some embodiments also provides formethods for selecting the ideal alkyl tail based at least upon thefollowing considerations: makeup of the photoactive composition (and/orits constituent parts, such as the identity of the primary electrondonor moiety), ability to be sublimed, and the characteristics of thesolvent, if any, into which the photoactive composition is to beemployed. These methods may in some embodiments be employed on theirown, or in other embodiments employed in connection with the methods forselecting a primary electron donor moiety and an electron withdrawingmoiety, discussed previously.

In some embodiments, the alkyl tail selection method comprises selectingan alkyl tail based in part upon the size of the primaryelectron-donating moiety of the photoactive composition. In someembodiments, this selection comprises selecting a longer alkyl tail(that is, an alkyl tail with a longer chain, whether or not that chainfurther comprises branches) to correspond to a larger primary electrondonor moiety. The method of some embodiments may further or insteadcomprise selecting a longer alkyl tail to correspond to a less polarsolvent, or selecting a shorter alkyl tail to correspond to a more polarsolvent. The method of other embodiments may further or instead compriseselecting a longer alkyl tail when the photoactive composition comprisesmore aromatic (ring) hydrocarbons.

FIG. 11 illustrates examples of molecular stacking resulting from thepresence of aromatic (ring) hydrocarbons in the photoactive composition.FIG. 11 is a molecular model of multiple molecules of a derivative ofthe composition T2 (of FIG. 7), but without the alkyl tails 705. FIG. 12illustrates examples of employing alkyl tails to provide intermolecularspacing among molecules of the photoactive composition (FIG. 12 is amolecular model of multiple molecules of the composition T2 of FIG. 7with diethyl alkyl tails 705 appended to the 9,9′ carbon of the fluorene701 of T2). This intermolecular spacing may be necessary to preventundesirable pi-pi stacking, the bonding interaction between two or moresets of pi-orbitals, which, may lead to detrimental clustering ofmultiple molecules of the photoactive composition, as depicted in FIG.13. FIG. 13 shows a stylized example of employment of photoactivecompositions as a dye on a DSSC. It depicts correctly aligned dyemolecules 1301 on a surface 1300 (e.g., TiO₂), as well as 1305 clustereddye molecules on the surface 1300. The alkyl tails of some embodimentsof the present disclosure prevent the undesirable clustering 1305,instead leading the dye molecules to maintain intermolecular spacing aswith the correctly aligned dye molecules 1301. In other embodiments forapplications such as BHJ, OPV, and FET, pi-pi stacking is desirable toinduce molecular ordering. In such a case, alkyl tails are used tocontrol the extent and direction of said pi-pi stacking. In someembodiments, the alkyl tail or tails provide advantageous intermolecularspacing when the composition is employed as a dye on a DSSC, BHJ, orhybrid OPV, as represented in FIG. 13 by the correctly aligned dyemolecules 1301, as compared to the clustered dye molecules 1305.

In embodiments in which the photoactive composition comprises more thanone alkyl tail, the alkyl tails may, in some embodiments, be identical.In other embodiments, they may be different. And in some embodiments,the alkyl tails may be appended to the same carbon atom of thephotoactive composition, while in other embodiments, the alkyl tails maybe appended to different carbon atoms of the photoactive composition.

Where the alkyl tails are different and bonded to the same carbon atom,however, chirality of the overall composition may result. Having isomersof different chirality intermixed may, in some cases, requirealternating molecules of different chiralty to achieve optimumintermolecular spacing. Thus, in some embodiments, the photoactivecomposition may comprise two or more different alkyl tails appended tothe same carbon such that it is chiral. Relatedly, some embodiments ofthe present disclosure may provide a method comprising isolatingmolecules of only one chirality (and a photoactive composition soisolated and thereby containing only molecules of one chirality). Otherembodiments may comprise molecules of mixed chirality, and otherembodiments may comprise a method of alternating the R- and S-isomers soas to achieve optimum intermolecular spacing. Further, yet otherembodiments may comprise a method of alternating any one or more of thefollowing: D isomers, L isomers, and diastereomers.

Primary Electron Donor Moiety

In some embodiments, the primary electron donor moiety comprises anelectron-donating group such as an amine (e.g., an amino substituent).In some embodiments, the primary electron donor moiety comprises an arylamine, such as a mono- or diaryl amine. In other words, suitable aminosubstituents may be of the general formula R₁R₂N—, where R₁ and R₂ mayor may not be equivalent chemical structures. For example, in someembodiments, R₁ and R₂ are both phenyls (e.g., a diphenylaminosubstituent). In other embodiments, R₁ may be a phenyl group and R₂ anaphthyl group (e.g., a napthyl-phenylamino, or naphthylanilino,substituent). In yet other embodiments, R₁ and R₂ may both be a napthylgroup (e.g., a dinaphthylamino substituent). Furthermore, although anynumber of isomers may be used in various embodiments, the amino group ofsome embodiments may comprise the 2-naphthyl anilino isomer (e.g., anN-(2-naphthyl)anilino substituent). In some embodiments, the primaryelectron donor moiety may comprise a diphenylamine substituent, and inother embodiments, the primary electron donor moiety may comprise anaphthyl triarylamine. Embodiments in which the primary electron donormoiety comprises either of these two classes of substituents may exhibitimproved properties by increasing the level of intramoleculardelocalization and due to pi-donation from these aromatic groups.

The primary electron donor moiety of other embodiments may comprise amonoaryl amino substituent, such as a methylphenylamino group (e.g., R₁is a methyl group and R₂ is a phenyl group), or a methylnaphthylaminogroup (e.g., R₁ is a methyl group and R₂ is a naphthyl group). R₁ may,in other embodiments, by ethyl, propyl, or any other moiety. It willadditionally be appreciated by one of ordinary skill in the art that anyother aryl amino or amino functional group can be used as the amine inembodiments wherein the electron donor moiety comprises an amine.

In other embodiments, the nitrogen (N) of the above-discussed aminocompounds may be substituted by another trivalent element from Group 15of the Periodic Table of the Elements. For example, in some embodiments,the nitrogen (N) may be substituted by phosphorous (P), arsenic (As), orantimony (Sb). That is, the primary electron donor moiety may comprise aphosphine (e.g., R₁R₂P—), an arsine (e.g., R₁R₂As—), or a stibine (e.g.,R₁R₂Sb—). The R₁ and R₂ of these compounds may be any of the compoundsdiscussed previously with respect to R₁R₂N. Thus, for example, theprimary electron donor moiety may comprise a monoaryl phosphine, or adiaryl phosphine (such as a napthyl-phenylphosphino) substituent.

In other embodiments the primary electron donor moiety may comprise adivalent substituent, such as an ether (of the general formula R—O—), asulfide (of the general formula R—S—), or a selenide (of the generalformula R—Se—). Again, the R of these formulae may be any of the R₁ orR₂ compounds discussed previously with respect to R₁R₂N.

In other embodiments, the primary electron donor moiety may comprise asubstituent selected from any one or more of the following categories:alkyl, phenyl, phenol, alkoxy phenyl, dialkoxy phenyl, alkyl phenyl, andmulticyclic aromatic substituents (e.g., naphthylene, anthracene).

Furthermore, in some embodiments, the primary electron donor moiety,regardless of its makeup, is at the opposing end of the composition fromthe electron-withdrawing moiety.

Selection of the primary electron donor moiety, with all othercomponents of the composition being otherwise identical, may in someembodiments result in different properties. For example, Table 1illustrates different HOMO, LUMO, E_(g), and dipole moment values thatresult when the primary electron donor moiety comprises: an aminesubstituent; a phosphine substituent; an arsine substituent; an ethersubstituent; a sulfide substituent; or a selenide substituent. Theamine, phosphine, and arsine substituents of Table 1 are of thestructure shown in FIG. 17 (wherein N and As are used in place of the P1701 of FIG. 17 for the amine and arsine, respectively); and the ether,sulfide, and selenide substituents of Table 1 are of the structure shownin FIG. 18 (wherein 0 and Se are used in place of the S 1801 of FIG. 18for the ether and selenide, respectively).

TABLE 1 Primary HOMO Dipole Moment Electron Donor Formula (eV) LUMO (eV)(debye) Amine C₃₇H₃₀N₂O₂ 5.08 2.44 5.26 Phosphine C₃₇H₃₀NO₂P 5.71 2.562.98 Arsine C₃₇H₃₀AsNO₂ 5.83 2.55 3.07 Ether C₃₁H₂₅NO₃ 5.69 2.48 3.84Sulfide C₃₁H₂₅NO₂S 5.65 2.57 3.01 Selenide C₃₁H₂₅NO₂Se 5.60 2.57 2.98

Thus, the present disclosure in some embodiments may further provide amethod for selecting the primary electron donor moiety based upon one ormore properties of the composition (e.g., HOMO, LUMO, and dipole moment)that would result, consistent with (or as part of) the design methoddiscussed previously and exemplified in FIG. 6. In some embodiments,this may comprise selecting a class of electron donor moiety (e.g.,amine, phosphine, arsine, ether, sulfide, selenide) based upon thegeneral qualities exhibited by that class of electron donor moiety.

Electron-Withdrawing Moiety

In some embodiments, the electron-withdrawing moiety may beelectron-poor. In some embodiments, it may be characterized by a higherelectron affinity relative to the electron donor moiety and the coremoiety. In other embodiments, the electron-withdrawing moiety mayadditionally be characterized by desirable electron orbital energylevels (e.g., HOMO/LUMO relative positions that provide advantageousorganic semiconducting capabilities, such as a desired band gap E_(g)).Thus, in some embodiments, the electron-withdrawing moiety may comprisea carboxylic acid group in order to exhibit both characteristics(electron affinity and desired HOMO/LUMO relative positions). Examplesof suitable carboxylic acid groups of some embodiments includecyanoacrylates. For example, FIG. 4 shows a photoactive compositionconsistent with the present disclosure in which the electron-withdrawingmoiety comprises a cyanoacrylate (i.e.,(Z)-2-cyano-3-[9,9′-diethyl-7-(N-phenylanilino)fluoren-3-yl]prop-2-enoicacid). In other embodiments, the electron-withdrawing moiety maycomprise any one of the following: a monocyanocomplex, a dicyanocomplex,a thiocyanocomplex, or an isothiocyanocomplex. For example, FIG. 5 showsthe photoactive composition2-[[9,9-diethyl-7-(N-phenylanilino)fluoren-2-yl]methylene]propanedinitrilein which the electron-withdrawing moiety comprises a dicyanocomplex, butis otherwise identical to FIG. 4.

Furthermore, in some embodiments, the electron withdrawing moiety mayfurther comprise a binding moiety; in other embodiments, the electronwithdrawing moiety may additionally serve as a binding moiety, withoutthe need to include a separate binding moiety. Thus, for example, inembodiments in which the electron withdrawing moiety comprises acarboxylic acid group, the carboxylic acid group may also function asthe binding moiety. In some embodiments, the binding moiety may serve tobind the photoactive composition of matter to another substance such asa substrate (e.g., TiO₂), for example in DSSC applications. The bindingmoiety may also, in some embodiments, serve to bind the photoactivecomposition to other substances including, but not limited to, Au, Ag,FTO (fluorine-doped tin oxide), ITO (indium tin oxide), or Nb₂O₅, as alayer or into supramolecular extended structures, such as metal organicframeworks, covalent organic frameworks, or crystalline structures.

Illustrative Embodiments of Photoactive Compositions and TheirTunability

Consistent with the above, then, in one embodiment the photoactivecompound may comprise2-cyano-3-[9,9′-diethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid in either the Z or E isomer (with reference to the C═C bond of thepropenoic acid). FIG. 7 shows the E isomer, labeled T2, that is,(E)-2-cyano-3-[9,9′-diethyl-7-(N-phenylanilino)fluoren-2-yl]prop-2-enoicacid. In this embodiment, the core moiety 701 comprises fluorene, withtwo C₂ alkyl tails 705 appended to the 9,9′ carbon of the fluorene (thatis, the core moiety comprises a 9,9′ diethyl fluorene). Theelectron-withdrawing moiety 710 comprises 2-cyanoprop-2-enoic acid, andis bonded at the 3 carbon of the propenoic acid to the core moiety. Theprimary electron donor moiety 715 here comprises an N-naphthylanilinosubstituent bonded to the 7 carbon of the fluorene. This embodimentspecifically comprises the N-(2-naphthyl)anilino isomer, which exhibitsthe unexpected benefit of greater photoelectric power conversionefficiency (PCE) (when the compound is used in OPV applications such asa DSSC dye) over a compound that comprises instead theN-(1-naphthyl)anilino isomer 801, but is otherwise identical, asillustrated in FIG. 8 (labeled T2-1-Naph). Specifically, compoundscomprising the N-(2-naphthyl)anilino isomer exhibit approximately 6.6%PCE, whereas otherwise identical compounds that instead employ theN-(1-naphthyl)anilino isomer exhibit approximately 6.0% PCE. Onepossible explanation for this enhanced efficiency is the significantelectronic change in the composition that results when the primaryelectron donor moiety comprises the N-(2-naphthyl)anilino isomer. Asshown in FIG. 9, the 2-naphthyl isomer T2 provides the composition witha superior (smaller) band gap (E_(g)) due to the resulting deeper LUMO(−2.44 eV vs vacuum) and shallower HOMO (−5.08 eV vs vacuum).Specifically, the 1-naphthyl E_(g) is 2.74 eV (again, this is thedifference between the LUMO and HOMO), while the 2-naphthyl E_(g) is2.64 eV, as shown in FIG. 9, which contains data derived fromcomputations in molecular modeling software. In addition, the 2-naphthylisomer additionally improves the absorptive properties of thecomposition, such as by red-shifting (e.g., permitting absorption oflonger wave-length light, increasing the spectral window).

This comparison further illustrates some of the desirable electronicproperties previously discussed with respect to tunabilityconsiderations, consistent with the design methods of variousembodiments of the present disclosure. That is, selection of the2-naphthyl isomer instead of the 1-naphthyl isomer results in smallerE_(g), shallower HOMO, deeper LUMO, and therefore smaller E_(g). This inturn has a positive effect on the PCE and on the absorptive propertiesof the composition.

Consistent with the above disclosure, other embodiments of compositionsof the present disclosure may comprise alkyl tails of differing lengths.For example, embodiments comprising the same electron-donating andelectron-withdrawing moieties, but different alkyl tails, include, butare not limited to:2-cyano-3-[9,9-dipropyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid;2-cyano-3-[9,9-dibutyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid; and so on up to and including C₁₀, C₁₅, C₂₀, C₃₀, or C₄₀ alkyltails, consistent with the previous discussion of alkyl tails. Theexample embodiment (E)2-cyano-3-[9,9-dihexyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid, for example, is labeled T2-C6 in FIG. 10, wherein the core moiety1001, electron-withdrawing moiety 1010, and primary electron donormoiety 1015 comprise the same substituents as the embodiment T2 depictedin FIG. 7. But, as shown in FIG. 10, the alkyl tails 1005 appended tothe 9,9′ carbon of the fluorene comprise a dihexyl substituent ratherthan the diethyl of T2 in FIG. 7. Similarly, FIG. 19 shows thesubstitution of C₂, C₁₀, and branched C₈ (ethylhexyl) alkyl tails on the9,9′ carbon of fluorene in various embodiments 1901, 1905, and 1910,respectively.

Embodiments using branched alkyl tails (and, again, utilizing the samecore, electron-donating, and electron-withdrawing moieties) include, butare not limited to:2-cyano-3-[9,9-dimethylethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid;2-cyano-3-[9,9-dimethylpropyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid; and so on using any branched alkyl tail.

As discussed previously, alkyl tails of differing lengths may providedifferent properties, such as greater intermolecular spacing. Continuingwith the example embodiment wherein the composition comprises2-cyano-3-[9,9-diethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid (that is, T2 of FIG. 7), FIG. 14 illustrates the molecular spacingdifference achieved when substituting 9,9′ dihexyl alkyl tails 1005 inT2-C6 for the 9,9′ diethyl alkyl tails 705 of T2 (11 Å versus 5 Å). Thisadditional spacing could, in some embodiments, prevent aggregation ofthe molecules of the compound, and thus result in higher deviceperformance when the compound is used in an OPV. This compositiondifference again further illustrates the additional tunabilityconsideration of intermolecular spacing, which may be taken into accountin the design methods of various embodiments previously discussed,particularly at the alkyl tail selection step.

As also discussed previously, in some embodiments alkyl tail selectionmay depend upon other factors in order to determine the optimum alkyltail. Table 2 below illustrates V_(OC) (open-circuit voltage), J_(SC)(Photocurrent density), Fill Factor (FF), and power conversionefficiency (PCE) for variations of the embodiment of FIG. 7 (that is,T2), employing different alkyl tails appended to the 9,9′ carbon of thefluorene.

TABLE 2 Alkyl Tail V_(OC) (mV) J_(SC) (mA/cm²) FF (%) PCE (%) 2C₂(diethyl) 780 10.7 68.5 5.70 2C₃ (dipropyl) 780 12.0 65.2 6.10 2C₄(dibutyl) 780 10.4 66.3 5.10 2C₅ (dipentyl) 753 11.3 60.0 5.10 2C₆(dihexyl) 728 10.4 66.0 5.00 2C₈ (dioctyl) 774 10.4 62.0 5.00 2C₁₀(didecyl) 780 11.8 56.0 5.16

In Table 2, the composition is used as a dye on an OPV, as illustratedin FIG. 15. FIG. 15 depicts various layers in a typical DSSC: substratelayer 1501 (glass in FIG. 15); electrode layer 1502 (shown as Pt/FTO(F-doped tin oxide)); electrolyte 1503; dye 1504; ML (mesoporous layer,which in some embodiments may be TiO₂) 1505; electrode layer 1506 (shownas FTO); and substrate layer 1507 (shown as glass in FIG. 15). In theinstances illustrated in Table 2, the composition is employed as a dye1504 in the absence of a light harvesting layer. A light-harvestinglayer may, in some embodiments, be employed to scatter incident light inorder to increase its path length through the photoactive layer andtherefore the light's probability of being absorbed.

Table 2 further demonstrates the relationship among PCE, V_(OC), J_(SC),and FF, which can be defined according to the following equation:

${PCE} = \frac{V_{OC} \times J_{SC} \times {FF}}{P_{0}}$where V_(OC), J_(SC), and FF are defined as above with respect to Table2, and P₀ is incident light power density in W/m².

In contrast, Table 3 presents the same data for the same composition T2(using varying alkyl tails appended to the 9,9′ carbon of the fluoreneof T2 as indicated in Table 3) when the composition is employed as a dye1504 with a Light Harvesting Layer 1601 added between the dye 1504 layerand the ML 1505, as represented in FIG. 16.

TABLE 3 Alkyl Tail V_(OC) (mV) J_(SC) (mA/cm²) FF (%) PCE (%) 2C₂(diethyl) 730 14.6 62.0 6.60 2C₃ (dipropyl) 713 14.2 61.1 6.20 2C₄(dibutyl) 720 13.0 60.0 5.60 2C₅ (dipentyl) 758 12.5 61.0 5.80 2C₆(dihexyl) 700 12.0 66.0 5.53 2C₈ (dioctyl) 780 11.8 63.0 5.80 2C₁₀(didecyl) 780 12.3 61.0 5.86

As can be seen, while C₃ alkyl tails provide the greatest PCE in theabsence of a light harvesting layer, C₂ alkyl tails provide the greatestPCE in the presence of a light harvesting layer. Thus, in someembodiments, the method of alkyl tail selection comprises selecting analkyl tail based in part upon the presence of a light harvesting layer,which is shown by Tables 2 and 3 to be an additional tunabilityconsideration consistent with the methods of various embodimentspreviously discussed. In other embodiments, the method of alkyl tailselection comprises selecting an alkyl tail based in part upon any oneor more device architectural feature(s), which are also tunabilityconsiderations.

It will further be appreciated by one of ordinary skill in the art thatother embodiments may comprise different primary electron-donatingmoieties and/or electron-withdrawing moieties consistent with theprevious discussion regarding each of those moieties. For example, FIG.4 shows another embodiment of a photoactive compound of the presentdisclosure:(Z)-2-cyano-3-[9,9′-diethyl-7-(N-phenylanilino)fluoren-2-yl]prop-2-enoicacid. In this instance, the core moiety 415, alkyl tails 410, andelectron-withdrawing moiety 405 are the same as in T2 of FIG. 7, but theprimary electron donor moiety 401 of the embodiment depicted in FIG. 4comprises an N-phenylanilino substituent instead of theN-(2-naphthyl)anilino substituent of the primary electron donor moiety715 of T2 in FIG. 7. And FIG. 5 shows an embodiment differing from theembodiment of FIG. 4 only in that the embodiment of FIG. 5 comprises adifferent electron-withdrawing moiety 505: 2-(methylene)propanedinitrileinstead of 2-cyano-prop-2-enoic acid (as in FIG. 4). And in someembodiments, the different primary electron donor moieties and/orelectron-withdrawing moieties may be selected based upon the methods ofdesign previously discussed.

Second and Additional Electron Donor Moieties

Referring back to FIG. 2, the photoactive compositions of someembodiments may further comprise a second electron donor moiety 5, whichin some embodiments is disposed between the core moiety 1 and theelectron-withdrawing moiety 3. The second electron donor moiety may, insome embodiments, serve to further tune the absorption window (i.e., theallowed absorption wavelengths based on the band gap) of thephotosensitive compositions of such embodiments. For example, in someembodiments, the second electron donor moiety may result in beneficialreduction of the band gap E_(g) between the HOMO and LUMO of thephotoactive composition. The second electron donor moiety may, in someembodiments, comprise a pi-electron donor. Any pi-electron donor moietyis suitable. FIG. 20, depicts various other embodiments of compositionsof the present disclosure, many of which include a second electron donormoiety. Specifically: T3 comprises a second electron donor moiety 2005comprising thiophene; T4 comprises a second electron donor moiety 2015comprising benzothiadiazole; T5 comprises a second electron donor moiety2025 comprising a phenyl moiety; T6 comprises a second electron donormoiety 2035 comprising benzothiophene; and T7 comprises a secondelectron donor moiety 2045 comprising thienothiophene. For comparison,T2 of FIG. 20 shows a photosensitive composition with no second electrondonor moiety, with the core moiety 2001 (a 9,9′-diethyl fluorene) bondeddirectly to the electron-withdrawing moiety 2002 (2-cyano prop-2-enoicacid) on the 3-carbon of the acid. T2 of FIG. 20 is also the embodimentT2 illustrated in FIG. 7, that is,(E)-2-cyano-3-[9,9-diethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid. Other examples of suitable second electron donor moieties include,but are not limited to: benzothiazole, benzothiophene, dibenzothiophene,naphthothiophene, dinaphthothiophene, benzonaphthothiophene,4H-cyclopenta[1,2-b:5,4-b′]bisthiophene, and thieno[3,2-b]thiophene.

Referring back to FIG. 20, the compositions T3, T4, T5, T6, and T7(comprising the second electron donor moieties discussed previously) mayexhibit smaller E_(g) values than exhibited in T2 (also shown in FIG.7), that is,(E)-2-cyano-3-[9,9-diethyl-7-[N-(2-naphthyl)anilino]fluoren-2-yl]prop-2-enoicacid. As shown in FIG. 21, the E_(g) of T3 is 2.37 eV; the E_(g) of T4is 1.98 eV; and the E_(g) of T5 is 2.44 eV, while the E_(g) of T2 is2.64 eV. And as shown in FIG. 22, the E_(g) of T6 is 2.22 eV, and theE_(g) of T7 is 2.28 eV. The data shown in FIGS. 21 and 22 were derivedfrom computations in molecular modeling software.

Accordingly, in some embodiments, the present disclosure furtherprovides for a method of selecting a second electron donor moiety basedupon the resulting effect on the HOMO and LUMO (and therefore band gapE_(g)) of the composition, consistent with (or in conjunction with) thedesign methods of various embodiments previously discussed. That is, insome embodiments, the second electron donor moiety selection step 607may comprise selection of a second electron donor moiety based at leastin part upon the resulting effect on the HOMO and LUMO (and thereforeband gap E_(g)) of the composition, as demonstrated for example in FIGS.21 and 22.

The compounds of some embodiments may comprise more than two electrondonor moieties. Third (and greater) electron donor moieties may beselected for addition to the compound according to any of the tunabilitycharacteristics discussed herein. For example, a third (or greater)electron donor moiety may be selected for addition to the compound inorder further to reduce E_(g), and/or to modify either or both of theHOMO and LUMO energy levels. Any moiety suitable as a primary or secondelectron donor moiety may be used as a third or greater electron donormoiety in these embodiments.

Second and Additional Electron-Withdrawing Moieties

The compounds of some embodiments may comprise a secondelectron-withdrawing moiety. In some embodiments, the secondelectron-withdrawing moiety may be any moiety suitable for inclusion asan electron-withdrawing moiety, as discussed previously. In otherembodiments, the second electron-withdrawing moiety may comprise asubstituent that is electron-poor, but is not suitable for binding thecompound to a substrate or other surface. That is, in these embodimentsit may be preferable to select the second electron-withdrawing moietyfrom a different subset of moieties than the subset from which the firstelectron-withdrawing moiety is selected. Thus, in some embodiments,second electron-withdrawing moieties may comprise any one or more of thefollowing: perfluorophenyls, acridones, triazines, and perylene imides.Some embodiments may also comprise three or more electron-withdrawingmoieties; these moieties may be selected from any moiety suitable foruse as a second electron-withdrawing moiety.

Synthesis

In other embodiments, the present disclosure provides for methods ofsynthesizing photosensitive compositions.

The process of one example embodiment is described as follows, and withreference to FIG. 23. Each step referred to herein may be accomplishedby any of various reaction mechanisms known in the art. Initially,fluorene is obtained by boiling asphaltene samples in ethanol to yield apale yellow solution. The solution is cooled and then filtered followedby concentration in boiling ethanol. The hot solution is allowed toslowly cool in sand or vermiculite to yield colorless crystals. Theobtained fluorene can be further purified, for example, by columnchromatography. The foregoing procedure is outlined in FIG. 23 as“Isolation” 2300. The fluorene is first converted into the 4,4′-dibromoderivative, labeled “Bromination” 2310. Next, appropriate alkyl tailsare added at the 9,9′ position of fluorene by formation of the fluoreneanion followed by addition of the selected alkylbromide, which include≧C₁ linear chains such as ethyl, n-propyl or n-decyl, or branched chainslike ethylhexyl, in “Alkylation” 2320. Following is the formation of thefluorene-arylamine in the 4-position of the fluorene by aBuchwald-Hartwig coupling with such primary electron donor moieties asdiphenylamine, naphthyl-phenylamine, or methylphenylamine, in “ArylCoupling” 2330. The aldehyde is next formed in the 4′ position of thefluorene by lithiation in N-formylpiperidine followed by acid quenching,as depicted by “Formulation” 2340. In addition, an electron withdrawingmoiety is added. Following the example set forth in FIG. 23, in “EWgroup addition” 2350, the cyanoacrylate complex is synthesized byreacting the previously formed aldehyde with cyanoacetic acid inrefluxing acetic acid with ammonium acetate promoter.

In some embodiments, “EW group addition” 2350 will determine or dependupon the intended or actual application of the photoactive compound.Thus, in some embodiments, synthesis of a dicyanocomplex instead of thecyanoacrylate complex previously referenced would be suitable for smallmolecule devices (e.g., OPVs, FETs, OLEDs), when R is CN in FIG. 23. Thecyanoacrylate complex formed in other embodiments, on the other hand,would be useful in DSSCs.

Applications

In other embodiments, the present disclosure provides for methods ofdetermining applications for the photosensitive compounds, and foremploying the compounds in a selected application. Thus, in someembodiments, the present disclosure provides method of application ofphotosensitive compounds to PVs. In some embodiments, once design andsynthesis of a photosensitive compound is completed, it may be tested todetermine the appropriate device structure for its application, as setforth previously and as shown in FIG. 6. Appropriate device structuresmay be, e.g., DSSC or BHJ, as shown in FIGS. 24 a and 24 b. FIG. 24 a isan illustration of a typical DSSC (shown with a light-harvesting layer),as depicted in FIG. 16. FIG. 24 b is an illustration of typical BHJdevice design, and includes: glass substrate 2401; ITO (tin-doped indiumoxide) strip 2402; interfacial layer 2403; photoactive layer 2404; andLiF/Al cathodes 2405. The materials of BHJ construction referred to aremere examples; any other BHJ construction known in the art may be usedconsistent with the present disclosure. In some embodiments, thecompositions of the present disclosure may be employed in thephotoactive layer 2404 of the BHJ, or in the dye layer 1504 of a DSSC.

Typical performance parameters of some embodiments can be seen in Table4 with PCE≈6.5% when T2 is employed as the DSSC dye 1504, and PCE≈1.4%when it is instead employed as the electron donor in the photoactivelayer 2404 of the BHJ. In some embodiments, such test data may at leastpartially form the basis for determining the application in which aphotoactive composition will be employed. Taking the example of T2, insuch embodiments it may be determined that T2 should be employed as aDSSC rather than a BHJ. In other embodiments, this test data may suggestfurther modification of T2 according to the design methods of thepresent disclosure, keeping in mind the relevant tunabilityconsiderations shown in Table 4 and discussed throughout thisdisclosure.

TABLE 4 Device V_(OC) (mV) J_(SC) (mA/cm²) FF (%) PCE (%) BHJ 780 3.7744.0 1.37 DSSC 734 10.7 65.5 6.48

The present disclosure in some embodiments likewise provides PVscomprising a photoactive compound of the present disclosure. In someembodiments, the PV may be an OPV. In some embodiments, the OPV may be aDSSC, wherein the dye comprises a photoactive compound of the presentdisclosure. In some embodiments, the OPV may be a BHJ, wherein thephotoactive layer of the BHJ comprises a photoactive compound of thepresent disclosure. Any DSSC, BHJ, or OPV generally as known in the artmay advantageously incorporate the compound of the present disclosure,which may provide substantial benefits over conventional OPVs,particularly greater PCE to cost ratios.

Some embodiments of the present disclosure may be described by referenceto the dye-sensitized solar cell depicted as stylized in FIG. 15,wherein the dye 1504 comprises a photoactive compound of the presentdisclosure. The cell may otherwise be comprised of any DSSC structureknown in the art, and otherwise function as known in the art. Thus, anexample DSSC as shown in FIG. 15 may be constructed according to thefollowing: electrode layer 1506 (shown as fluorine-doped tin oxide, FTO)is deposited on a substrate layer 1507 (shown as glass). Mesoporouslayer ML 1505 (which may in some embodiments be TiO₂) is deposited ontothe electrode layer 1506, then the photoelectrode (so far comprisingsubstrate layer 1507, electrode layer 1506, and mesoporous layer 1505)is soaked in a solvent (not shown) and dye 1504 comprising a photoactivecompound of the present disclosure. This leaves the dye 1504 bound tothe surface of the ML. A separate counter-electrode is made comprisingsubstrate layer 1501 (also shown as glass) and electrode layer 1502(shown as Pt/FTO). The photoelectrode and counter-electrode arecombined, sandwiching the various layers 1502-1506 between the twosubstrate layers 1501 and 1507 as shown in FIG. 15, and allowingelectrode layers 1502 and 1506 to be utilized as a cathode and anode,respectively. A layer of electrolyte 1503 is deposited either directlyonto the completed photoelectrode after dye layer 1504 or through anopening in the device, typically a hole pre-drilled by sand-blasting inthe counter-electrode substrate 1501. The cell may also be attached toleads and a discharge unit, such as a battery (not shown), as is knownin the art. Substrate layer 1507 and electrode layer 1506, and/orsubstrate layer 1501 and electrode layer 1502 should be of sufficienttransparency to permit solar radiation to pass through to thephotoactive dye 1504. In some embodiments, the counter-electrode and/orphotoelectrode may be rigid, while in others either or both may beflexible. The substrate layers of various embodiments may comprise anyone or more of: glass, polyethylene, PET, Kapton, quartz, aluminum foil,gold foil, and steel.

Other example embodiments may comprise a PV that comprises a photoactivelayer comprising a photoactive compound of the present disclosure. Suchembodiments may be described by reference to FIG. 26, which shows atypical PV cell 2610 including a transparent layer 2612 of glass (ormaterial similarly transparent to solar radiation) which allows solarradiation 2614 to transmit through the layer. The transparent layer ofsome embodiments may comprise any one or more of a variety of rigid orflexible materials such as: glass, polyethylene, PET, Kapton, quartz,aluminum foil, gold foil, or steel. The active layer 2616 is composed ofelectron donor or p-type material 2618 and electron acceptor or n-typematerial 2620. Compositions of the present disclosure may be used aseither the p- or n-type material or both p- and n-type materials in asingle device embodiment. The photo-active layer 2616 is sandwichedbetween two electrically conductive electrode layers 2622 and 2624, asis known in the art. In FIG. 26, the electrode layer 2622 is an ITOmaterial. The electrode layer 2624 is an aluminum material. Othermaterials may be used as is known in the art. The cell 2610 alsoincludes an interfacial layer 2626, shown as a PEDOT:PSS material. Theinterfacial layer may assist in charge separation. In some embodiments,the interfacial layer may comprise a compound of the present disclosureinstead of or in addition to the photoactive layer comprising a compoundof the present disclosure. There is also an interfacial layer (IFL) 2627on the aluminum-cathode side of the device. In some embodiments, the IFL2627 on the aluminum-cathode side of the device may comprise a compoundof the present disclosure instead of or in addition to either or both ofthe photoactive layer and the interfacial layer 2626 comprising acompound of the present disclosure. A typical architecture issubstrate-anode-IFL-photoactive layer-IFL-cathode, wherein thephotoactive layer comprises a compound of the present disclosure. Otherlayers and materials may be utilized in the cell as is known in the art.The cell 2610 is attached to leads 2630 and a discharge unit 2632, suchas a battery, as is known in the art.

In other embodiments, the present disclosure provides hybridorganic-inorganic PVs comprising photoactive compounds of the presentdisclosure. FIG. 27 shows an exploded representational view of a samplePV cell having a transparent conducting electrode 2780, an electronblocking layer 2782, a p-type thin film active layer 2684, an n-typeorganic active layer 2786, a hole blocking layer 2788 and a low workfunction layer as an electrode 2790. As shown, the n-type organic layercomprises a photoactive compound of the present disclosure while thep-type layer is inorganic. In other embodiments, the p-type layercomprises a photoactive compound of the present disclosure while then-type layer is inorganic.

In other embodiments, the present disclosure provides solid state DSSCscomprising photoactive compounds of the present disclosure. Someembodiments of these solid state DSSCs may be described by reference toFIG. 28, which is a schematic of a typical solid state DSSC cell. Aswith the example solar cell depicted in, e.g., FIG. 26, an active layercomprised of p- and n-type active material (2810 and 2815, respectively)is sandwiched between electrodes 2805 and 2820 (shown in FIG. 28 asPt/FTO and FTO, respectively). In the embodiment shown in FIG. 26, thep-type active material comprises a solid electrolyte (otherwise known asa hole-transport material); the n-type active material comprises TiO₂coated with a dye; and the dye comprises a photoactive compound of thepresent disclosure. Substrate layers 2801 and 2825 (both shown in FIG.28 as glass) form the respective external top and bottom layers of theexemplar cell of FIG. 28. These layers may comprise any material ofsufficient transparency to permit solar radiation to pass through to thephotoactive layer comprising p- and n-type active material 2810 and2815, such as glass, polyethylene, PET, Kapton, quartz, aluminum foil,gold foil, and/or steel. Furthermore, in the embodiment shown in FIG.28, electrode 2805 (shown as Pt/FTO) is the cathode, and electrode 2820is the anode. As with the exemplar solar cell depicted in FIG. 26, solarradiation passes through substrate layer 2825 and electrode 2820 intothe active layer, whereupon at least a portion of the solar radiation isabsorbed so as to produces one or more excitons to enable electricalgeneration according to mechanisms known in the art. The p-type activematerial 2810 may in some embodiments comprise a solid electrolyte. Insome embodiments, it may be CsSnI₃, or poly(3-hexylthiophene),spiro-OMeTAD, or any solid p-type material. The solid state DSSCs ofsome embodiments may comprise a solid state layer in the absence of aliquid electrolyte. Further, the solid state layer (such as CsSnI₃) ofsome embodiments may be internally located in the DSSC (that is, locatedbetween the electrodes of the DSSC, as shown in FIG. 28). The p-type andn-type active materials of other embodiments are reversed. That is, insome embodiments, any suitable p-type material may instead be used asn-type material, and vice versa. A solid state DSSC according to someembodiments may be constructed in a substantially similar manner to thatdescribed above with respect to the DSSC depicted as stylized in FIG.15. In the embodiment shown in FIG. 28, p-type active material 2810corresponds to electrolyte 1503 of FIG. 15; n-type active material 2815corresponds to both dye 1504 and ML 1505 of FIG. 15; electrodes 2805 and2820 respectively correspond to electrode layers 1502 and 1506 of FIG.15; and substrate layers 2801 and 2825 respectively correspond tosubstrate layers 1501 and 1507.

Employing a photoactive composition of the present disclosure in a solidstate DSSC may, in some embodiments, significantly expand the freedom todesign the photoactive composition. For instance, in some embodiments, asolid-state layer may advantageously permit a photoactive composition toobtain a shallower HOMO energy level while still maintaining electricalconductivity between the solid-state layer and the photoactivecomposition. FIG. 29 is a representation of relative energy levels in eVof various components of an exemplar solid state DSSC system that uses asolid-state layer (comprising in this example CsSnI₃). The data shown inFIG. 29 was derived from empirical results such as cyclic voltammetry orultraviolet photoelectron spectroscopy. Comparison between FIG. 29 andFIG. 25 shows that the exemplar solid state DSSC of FIG. 29 uses theCsSnI₃ in place of the iodide electrolyte of FIG. 25. FIG. 29 shows theshallower HOMO energy level permitted by use of CsSnI₃ (4.92 eV ascompared to the 5.34 eV value of iodide electrolyte reduction I₂ ⁻→I₃⁻). That is, the photoactive compound T2 of FIG. 29 could be altered(for example, by the design methods of the present disclosure previouslydiscussed) so as to achieve a shallower HOMO, unlike the photoactivecompound T2 of FIG. 25, where the relatively deeper eV value of theiodide electrolyte reduction I₂ ⁻→I₃ ⁻ provides an upper limit on theHOMO energy level of the photoactive compound T2, as explainedpreviously. Alternatively, in other embodiments, a different photoactivecompound consistent with the present disclosure may be used, wherein thedifferent photoactive compound has a shallower HOMO energy level. Forexample, FIG. 30 shows a different photoactive compound C36 with a muchshallower HOMO (4.98 eV) advantageously employed in the DSSC of thisembodiment using a CsSnI₃ solid-state layer. The data shown in FIG. 30was derived from empirical results such as cyclic voltammetry orultraviolet photoelectron spectroscopy. FIG. 31 shows the structure ofC36, which is(E)-2-cyano-3-[6-[9,9-diethyl-7-(4-methoxy-N-(4-methoxyphenyl)anilino)fluoren-2-yl]benzothiophen-2-yl]prop-2-enoicacid.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. In particular, every range of values(of the form, “from about a to about b,” or, equivalently, “fromapproximately a to b,” or, equivalently, “from approximately a-b”)disclosed herein is to be understood as referring to the power set (theset of all subsets) of the respective range of values, and set forthevery range encompassed within the broader range of values. Also, theterms in the claims have their plain, ordinary meaning unless otherwiseexplicitly and clearly defined by the patentee.

What is claimed is:
 1. A photovoltaic device comprising: a firstelectrode; an active layer comprising a photoactive organic compound;and a second electrode; wherein the active layer is between the firstand second electrodes; wherein the photoactive organic compoundcomprises: a primary electron donor moiety comprising at least onesubstituent selected from the group consisting of: aryl amine; arylphosphine; aryl arsine; aryl stibine; aryl sulfide; aryl selenide;phenyl; phenol; alkoxy phenyl; dialkoxy phenyl; alkyl phenyl, and anycombination thereof; a core moiety comprising at least one arylsubstituent selected from the group consisting of: benzothiophene,dibenzothiophene, naphthothiophene, dinaphthothiophene,benzonaphthothiophene, naphthyl, benzothiazole,benzo[b]naphtha[2,3-d]thiophene,4H-cyclopenta[1,2-b:5,4-b′]bisthiophene, dinaphtho[2,3-d]thiophene,thieno[3,2-b]thiophene, naphthalene, anthracene, and any combinationthereof; a second electron donor moiety comprising at least onepi-electron donor substituent selected from the group consisting of:thiophene, benzene, benzothiophene, thienothiophene; and any combinationthereof; and an electron-withdrawing moiety comprising at least onesubstituent selected from the group consisting of: a carboxylic acid; amonocyanocomplex; a dicyanocomplex; a thiocyanocomplex; anisothiocyanocomplex, and any combination thereof.
 2. The photovoltaicdevice of claim 1 wherein the active layer comprises one or both of ap-type material and an n-type material; and wherein at least one of thep-type and the n-type material comprises the photoactive organiccompound.
 3. The photovoltaic device of claim 1 wherein the active layercomprises an electrolyte and a dye; wherein the dye comprises thephotoactive organic compound.
 4. The photovoltaic device of claim 1wherein the active layer comprises a hole-transport material and a dye;wherein the dye comprises the photoactive organic compound.
 5. Thephotovoltaic device of claim 2 wherein the primary electron donor moietycomprises a multi-aryl amine.
 6. The photovoltaic device of claim 2wherein the core moiety comprises at least one aryl substituent sourcedfrom asphaltene.
 7. The photovoltaic device of claim 3 wherein theprimary electron donor moiety comprises a multi-aryl amine.
 8. Thephotovoltaic device of claim 3 wherein the core moiety comprises atleast one aryl substituent sourced from asphaltene.
 9. The photovoltaicdevice of claim 4 wherein the primary electron donor moiety comprises amulti-aryl amine.
 10. The photovoltaic device of claim 4 wherein thecore moiety comprises at least one aryl substituent sourced fromasphaltene.
 11. The photovoltaic device of claim 2 wherein the primaryelectron donor moiety comprises a dialkoxyphenylamine.
 12. Thephotovoltaic device of claim 2 wherein the core moiety comprises adibenzothiophene.
 13. The photovoltaic device of claim 11 wherein thecore moiety comprises a dibenzothiophene.
 14. The photovoltaic device ofclaim 13 wherein the photoactive organic compound has the structuralformula:

wherein R comprises the second electron donor moiety and theelectron-withdrawing moiety.
 15. The photovoltaic device of claim 3wherein the primary electron donor moiety comprises adialkoxyphenylamine.
 16. The photovoltaic device of claim 3 wherein thecore moiety comprises a dibenzothiophene.
 17. The photovoltaic device ofclaim 16 wherein the core moiety comprises a dibenzothiophene.
 18. Thephotovoltaic device of claim 17 wherein the photoactive organic compoundhas the structural formula:

wherein R comprises the second electron donor moiety and theelectron-withdrawing moiety.
 19. The photovoltaic device of claim 4wherein the primary electron donor moiety comprises adialkoxyphenylamine.
 20. The photovoltaic device of claim 4 wherein thecore moiety comprises a dibenzothiophene.
 21. The photovoltaic device ofclaim 20 wherein the core moiety comprises a dibenzothiophene.
 22. Thephotovoltaic device of claim 17 wherein the photoactive organic compoundhas the structural formula:

wherein R comprises the second electron donor moiety and theelectron-withdrawing moiety.
 23. A photovoltaic device comprising: afirst electrode; an active layer comprising a photoactive organiccompound; and a second electrode; wherein the active layer is betweenthe first and second electrodes; and wherein the photoactive organiccompound has the structural formula:


24. The photovoltaic device of claim 23 wherein the active layercomprises one or both of a p-type material and an n-type material; andwherein at least one of the p-type and the n-type material comprises thephotoactive organic compound.
 25. The photovoltaic device of claim 23wherein the active layer comprises an electrolyte and a dye; wherein thedye comprises the photoactive organic compound.
 26. The photovoltaicdevice of claim 23 wherein the active layer comprises a hole-transportmaterial and a dye; wherein the dye comprises the photoactive organiccompound.